Large constellations of bright artificial satellites in low Earth orbit pose significant challenges to ground-based astronomy ¹. Current orbiting constellation satellites have brightnesses between apparent magnitudes 4 and 6, whereas in the near-infrared Ks band, they can reach magnitude 2 (ref. ²). Satellite operators, astronomers and other users of the night sky are working on brightness mitigation strategies ^3,4. Radio emissions induce further potential risk to ground-based radio telescopes that also need to be evaluated. Here we report the outcome of an international optical observation campaign of a prototype constellation satellite, AST SpaceMobile’s BlueWalker 3. BlueWalker 3 features a 64.3 m ² phased-array antenna as well as a launch vehicle adaptor (LVA) ⁵. The peak brightness of the satellite reached an apparent magnitude of 0.4. This made the new satellite one of the brightest objects in the night sky. Additionally, the LVA reached an apparent V-band magnitude of 5.5, four times brighter than the current International Astronomical Union recommendation of magnitude 7 (refs. ^3,6); it jettisoned on 10 November 2022 (Universal Time), and its orbital ephemeris was not publicly released until 4 days later. The expected build-out of constellations with hundreds of thousands of new bright objects ¹ will make active satellite tracking and avoidance strategies a necessity for ground-based telescopes.

Meaningful SSA work on earth-orbiting satellites can be done on a shoe-string budget, with modest, off the shelf equipment. This has been shown by an informal group of self-funded Independent Space Observers (“ISO’s”) organized around the Seesat-L mailing list. Literally from their backyards, they track some 200 “classified” objects – objects that are not in the public orbital catalogues – using very simple equipment: from binoculars and stopwatch on the ‘old skool’ end, to DSLR’s or sensitive CCTV or CMOS/CCD cameras with fast photographic lenses and GPS time control on the sophisticated end. In this paper, a brief outline is provided on the techniques and equipment used by Seesat-L members and an example is given on how a new 'classified' launch is located and tracked, often within hours of launch. It is discussed why the whole concept of keeping the orbits of certain space assets “classified” is problematic: not only is it unrealistic, but it also goes against core notions of transparency and accountability regarding activities in space.